Many ceramic products are configured from a ceramic portion, which is a functional and structural member, and an electrode portion made of metal. Examples of combinations of such ceramic products and electrode portions include stacked ceramic capacitors (Ni, Pd, Pt electrodes), LTCC components (Ag, Cu, Ag—Pd electrodes), piezo actuators (Pd electrode), semiconductor packages (W electrode), and spark plugs (Ir, Pt electrodes).
However, firing of Ni, Cu, and W with the ceramic portion requires atmosphere control, which makes it difficult to obtain the intended performance of the ceramic portion. Another problem is the high manufacturing cost. On the other hand, since the melting point of Ag is low (962° C.), the type of applicable ceramics becomes limited, and further, the low-temperature firing may impair the ceramic properties. Further, noble metal materials such as Pd, Ir, and Pt are expensive, and thus, are not easily applicable to electrodes that require large areas.
Meanwhile, as an example of an oxide for use in ceramic portions, there is known a lanthanum cobalt oxide having a negative resistance temperature property which shows high resistance values at an ordinary temperature and in which the resistance value decreases with increasing temperatures (Patent Literatures 1 and 2). Further, the electrically conductive oxide of the Patent Literature 2 has a high resistance value near room temperature, and moreover, has a B-value with a small gradient near room temperature, and has the B-value with a large gradient at high temperatures.